Amazon’s Elastic Cloud is a huge collection of computing power in web-connected data centers. It hosts the web sites of a bunch of businesses and is the backbone of the web services economy, making it cheap for startups to launch and scale up a web site without having to build their own data centers.

The outage that started last night showed the vulnerability of this model, even though Amazon has backup technology in place. No word just yet on what caused the outage and what services are back up and running. So far, it looks like Scvngr is down and Foursquare is pretty slow.